The dobby and the reversible Jacquard machine differ with respect to the control among others in that the former one follows the classic weft-logic method of operation while the latter one has, in the case of a change in the direction of rotation, only after at least one weft has run off, the logical shed formation. These basic different characteristics can be observed during the weft searching function at which time the machine group is rotated both forwardly and also in reverse over a sequence of wefts. Because of a reversal in the direction of rotation of a weaving machine with the two shed-forming machines which are each controlled by one pattern card, the pattern card of one of the two machines must be adjusted manually for the mentioned reason so that both at a given time simultaneously open the same shed. Such an action, which must take place twice per weft operation, is not only time consuming, but leads in the case of an erroneous manipulation or forgotten adjustment to a serious breakdown in the synchronous run of the two shed-forming machines.
In order to eliminate breakdowns in the synchronous run of both shed-forming machines and to simplify the weft searching operation and to handle it quicker, it has been suggested to control both machines by one single pattern card which is built into the Jacquard machine, wherein the control impulses are transmitted therefrom by means of harness cords to the dobby.
Such an arrangement is described in German OS No. 2,256,636, wherein the demand for a synchronous run at any desired change in the direction of rotation due to a weft searching operation is not met in the sense of the mentioned objective.
The purpose of the invention is to drivingly connect both shed-forming machines nonchangably and synchronously to the main shaft of the weaving machine and to control them together from the Jacquard pattern card so that for weft searching, the main shaft together with the two shed-forming machines are rotated back for taking out one or several successive weft threads and the latest after two rotations, the machine group opens the desired shed or the shed row. After the weft searching has taken place in the reverse run, the shed of the last removed weft thread is adjusted again for further weaving in the forward direction, the latest after two shaft rotations, without necessitating during the entire weft search a manual adjustment of the pattern card for the needs of the dobby. The efficiency of the machine is therewith increased by a quicker weft search and by avoiding weaving errors.
This is made possible with a weaving machine of the abovementioned type, which is characterized inventively by a corresponding shed opening taking place in a common reverse rotation and subsequent forward rotation of the two shed-forming machines without requiring a manual adjustment of the control mechanism.
Thus the solution is to control each frame-lift unit of each four hooks and four harness cords of the Jacquard machine in such a manner that two cords transmit the control impulses for the new weft and two cords transmit the impulses for the passed weft into the dobby one time during each rotation of the weaving machine, wherein on the input side of the dobby a known needle device having, on the one hand, four reading needles is influenced or, on the other hand, each of two known control levers of a cam-controlled dobby unit is controlled by one clasp handle for the new weft and each clasp handle for the passed weft into one of two possible end positions, and between the cord and the reading needle there is inserted a pawlless impulse converter or rather between two clasp handles and one control lever or draw hook there is inserted a rocker arm for two end positions for the control or release function, so that a control impulse which is introduced into the dobby at any desired time is passed on at a given time.